EXCRETION AND WATER BALANCE 45 



earthworms and the results are worth recording as a guide to 

 what we may expect to happen in leeches. 



Various workers have made physiological observations on 

 slices of earthworm intestine with chloragogenous tissue attached. 

 Cohen and Lewis (1949) showed that large quantities of ammonia 

 are found there and that arginase is present. Heidermanns (1937) 

 found that this tissue converts peptone to urea and called the 

 chloragogenous tissue '' the central organ of urea metabolism." 

 Bahl (1947) found, in addition to ammonia and urea, creatinine 

 which is presumably produced by muscular tissue. Florkin (1935) 

 showed the presence of xanthine-oxidase. These results clearly 

 indicate that ammonia is being converted to urea by the Krebs 

 cycle involving the production of arginine and its conversion to 

 urea and ornithine with the aid of arginase ; further, that uric acid 

 synthesis by the oxidation of xanthine or hypoxanthine is occurring 

 in the tissue slices. Semal-van Gansen (1956) also showed that the 

 chloragogen cells are the site of glycogen metabolism and fat 

 storage and contain abundant acid phosphatase. She drew atten- 

 tion to the similarity in function between chloragogenous tissue 

 and vertebrate liver. 



It has long been known that chloragogen cells of earthworms 

 accumulate large numbers of yellowish refringent granules which 

 are insoluble in acids or alkalis (except ammonia) at ordinary 

 temperatures. Semal-van Gansen found that in Allolobophora 

 caliginosa these are made up of a purine, probably a heteroxanthine 

 such as 7-methyl xanthine, together with a chromolipid and a 

 small amount of mica. Roots (1960) working with Lumhricus 

 terrestris could find no purine. During starvation the chloragogen 

 cells retain their granules but give up glycogen and fat droplets 

 from the cytoplasm. It is now abundantly clear that earthworm 

 chloragogenous tissue is the main site of deamination and storage 

 of carbohydrates and fats. The waste products of metabolism are 

 ammonia and urea, which are presumably liberated into the 

 coelomic fluid, and possibly a purine which is accumulated in 

 granular form, to be liberated into the coelom at the breaking up 

 of the chloragogen cell. Particulate material in the coelomic fluid 

 may be ingested by coelomic corpuscles and disposed of in various 

 ways. It may be deposited in the body wall as pigment, deposited 

 as brown bodies in the posterior part of the worm or carried 



